I didnt quite get it either. They tell you in the plans that they choose to use shorter rivets and they are "adequate" for the use there but they will at least in my experience never pass the rivet checker guage. the ones with the hinge brackets call for -7 and should be an -8 in my opinion.
VAF dues paid until 05/2018
RV7 - Working on empennage 95% done
RV7 - Wings arrived and inventoried...
Cessna Rocket 210HP - Best dang 172 Ever made! (sold)